Restoration of Pulsatile Flow Reduces Sympathetic Nerve Activity Among Individuals With Continuous-Flow Left Ventricular Assist Devices
Background—Current-generation left ventricular assist devices (LVAD) provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex.
Methods and Results—Ten male and three female subjects (54±14 years) with Heartmate II, continuous-flow (CF) LVADs underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200-400 RPM) in CF-LVAD pump speed from a maximum of 10,480±315 RPM to a minimum of 8,500±380 RPM. Reductions in pump speed led to increases in pulse pressure (high v. low speed: 17±7 v. 26±12mmHg, P<0.01), distension of the carotid artery and carotid arterial wall tension (P<0.05 for all measures). In addition, MSNA was reduced (high v. low speed: 41±15 v. 33±16 bursts/min, P<0.01) despite a reduction in MAP and was inversely related to pulse pressure (P=0.037).
Conclusions—Among subjects with CF-LVADs, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Further study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.
- Received May 22, 2015.
- Revision received August 24, 2015.
- Accepted September 10, 2015.